Adjustable spark plug



P. T. WOLCOTT ADJUSTABLE SPARK PLUG Filed Nov.

June 18, 1968 ullll-l INVENTOR.

Paul T. Wolcoti ATTORNEY United States Patent O 3,389,287 ADJUSTABLE SPARK PLUG Paul T. Wolcott, 740 E. Michigan, Marshall, Mich. 49068 Filed Nov. 28, 1966, Ser. No. 597,417 4 Claims. (Cl. 313-125) This invention relates to the construction of adjustable spark plugs. The proper functioning of an internal combustion engine requires that .the spark gap of an ignition system be maintained within specied limits. The erosion and burning of electrodes produces a progressive tendency to increase the gap, and periodic adjustment must be made in order to maintain the elective and eicient operation of the engine. The setting and adjustment of the gap of conventional lixed spark plugs has been done while the plugs were removed from the engine. It has long been recognized that it would be desirable to perform this operation while the engine was running, or at least without having to remove the plugs from the engine. Exteriorly-adjustable spark plugs have been devised in various forms, `some of these appearing in the following United States patents:

Songer, 2,195,543, 1940 McDonald, 2,540,453, 1951 Thomas, 2,616,407, 1952 Berstler, 2,626,595, 195-3 Ross, 3,145,319, 1964 rIhe practical problems of manufacturing cost, prevention of leakage, and the prevention of short circuiting have not been effectively solved by any of the adjustable spark plugs known to applic-ant. The present invention provides a structure centering in a sub-assembly of the conductive components, with this sub-assembly being neatly received within separable ceramic insulating elements. This structure produces the simplicity of assembly required by cost considerations, and is also easily sealed. Adjustment is accomplished by a standard Allen wrench, with gloves or insulation being used by the mechanic if the adjustment is to be made while the engine is running. The several features of the invention will be analyzed in detail through a discussion of the particular embodiment illustrated in the accompanying drawing. In the drawing:

FIGURE 1 is a perspective side elevation of a spark plug embodying this invention.

FIGURE 2 is an axial section on an enlarged scale over that of FIGURE 1, showing the position of an Allen wrench prior to insertion for making the adjustment.

FIGURE 3 is an exploded view showing the separated components of the structure shown in FIGURE 2.

Referring to the drawing, the steel housing 10 has an annular lip 11 initially formed as an upwardly-extending ring. After the assembly of the interior components, the lip 11 is deformed into the position shown in FIG- URE 2 to retain the components in assembled relationship. The housing has a tubular threaded lower portion 12 adapted for engagement with an internal combustion engine, with the lower open extremity provided with a diametral electrode bar 13.

The electrically conductive portion of the spark plug is a series of components, most of which are preferably formed of brass. The upper tubular member 14 has a ange 15 received on the shoulder 16 of the sleeve 17. The lower tubular portion 18 has a flange 19 received against the shoulder 20 at the underside of the sleeve 17. Prior to the assembly of the lower tubular member 18 to the sleeve 17, the adjustable electrode member 21 is placed in threaded engagement with the inside threading of the sleeve 17. The electrode member 21 has a lower ex- 3,389,287 Patented June 18, 1968 tension 22 of conventional electrode allo which extends through the tubular portion 18 with a very close tit to assure bearing for electrical contact. After the electrode 21 is assembled to the sleeve 17, and the upper and lower tubular members correspondingly placed in position, the upper and lower ends of the sleeve 17 are rolled over as shown in FIGURE 2 to retain the conductive components in an integral sub-assembly.

The upper and lower ceramic portions 23 and 24 may then be slipped over the opposite ends of the conductive sub-assembly, and placed within the housing 10 as shown in FIGURE 2. The seal rings 25 and 26 are used to cushion the ceramic members at the pressure points provided by the housing 10, and the intermediate seal 27 is placed between the axially opposite ends of the ceramic members Z3 and 24 to eliminate the possibility of short circuiting through any gap that might exist at this point. The lip 11 is rolled down with sufficient pressure to hold the components solidly in the FIGURE 2 position with a selected amount of pressure which can. be tolerated by the ceramic materials.

The resulting assembly provides a tubular passageway indicated at 28 through which the Allen wrench 29 can be inserted into the wrench recess 30 at the top of the adjustable electrode 21. These components are in axial alignment, and rotation of the Allen wrench, after the Wrench has been engaged with the recess 30, will produce a tendency for the extension Z2 to approach or withdraw from the diametral grounding electrode 13, thus adjusting the gap of the spark plug. If desired, a conductive cap of the type shown at 31 may be added to the assembly through engagement at the threaded upper extremity 32 of the upper tubular member 14. It is preferable that any connection to the cap 30 be from a lateral direction, so that the passage 28 will not be obstructed. If this form of connection is used, adjustment of the gap of the plug may be made while the engine is running, with the plug tiring as under normal operating conditions.

The particular embodiments of the present invention which have been illustrated and discussed herein are illustrative only and are not to be considered as a limitation upon the scope of the appended claims. In these claims, it is my intent to claim the entire invention disclosed herein, except as I am limited by the prior art.

I claim:

1. A spark plug comprising:

a metal housing having a downwardly open tubular threaded portion for engagement with an engine, and also having a diametral electrode bar across the end of said threaded portion;

irst and second ceramic members having at least portions thereof received within said housing, said ceramic members being separable on Ia plane perpendicular to the axis of said threaded portion, and said ceramic members each having an axial bore and together defining a central recess;

a sleeve of conductive material having a threaded inside diameter, and disposed within said recess;

a lower tubular member coaxial with and secured with respect to said sleeve, and extending within the axial bore of one of said ceramic members;

an upper tubular` member of conductive material coaxial with and secured with respect to said sleeve, and extending within the axial bore of the other of said ceramic members; and

an adjustable electrode having a portion extending within -said lower tubular member in closely fitting relationship, and through said axial bore associated therewith, said electrode having a threaded portion in engagement `with said sleeve, said electrode having a wrench recess in the top surface thereof in axial alignment.

2. A spark plug as dened in claim 1, wherein said upper and lower tubular members have flanges secured to said sleeve.

3. A Spark plug as dened in claim 1, wherein said lower tubular member is of conductive material and bears on said adjustable electrode.

4. A spark plug as defined in claim 1, wherein said ceramic members are separated by a seal.

4 References Cied UNlTED STATES PATENTS 698,042 4/1902 Mosler 313-125 5 DAVID J. GALVIN, Primary Examiner.

JAMES W. LAWRENCE, Examiner. 

1. A SPARK PLUG COMPRISING: A METAL HOUSING HAVING A DOWNWARDLY OPEN TUBULAR THREADED PORTION FOR ENGAGEMENT WITH AN ENGINE, AND ALSO HAVING A DIAMETRAL ELECTRODE BAR ACROSS THE END OF SAID THREADED PORTION; FIRST AND SECOND CERAMIC MEMBERS HAVING AT LEAST PORTIONS THEREOF RECEIVED WITHIN SAID HOUSING, SAID CERAMIC MEMBERS BEING SEPARABLE ON A PLANE PERPENDICULAR TO THE AXIS OF SAID THREADED PORTION, AND SAID CERAMIC MEMBERS EACH HAVING AN AXIAL BORE AND TOGETHER DEFINING A CENTRAL RECESS; A SLEEVE OF CONDUCTIVE MATERIAL HAVING A THREADED INSIDE DIAMETER, AND DISPOSED WITHIN SAID RECESS; A LOWER TUBULAR MEMBER COAXIAL WITH AND SECURED WITH RESPECT TO SAID SLEEVE, AND EXTENDING WITHIN THE AXIAL BORE OF ONE OF SAID CERAMIC MEMBERS; AN UPPER TUBULAR MEMBER OF CONDUCTIVE MATERIAL COAXIAL WITH AND SECURED WITH RESPECT TO SAID SLEEVE, AND EXTENDING WITHIN THE AXIAL BORE OF THE OTHER OF SAID CERAMIC MEMBERS; AND AN ADJUSTABLE ELECTRODE HAVING A PORTION EXTENDING WITHIN SAID LOWER TUBULAR MEMBER IN CLOSELY FITTING RELATIONSHIP, AND THROUGH SAID AXIAL BORE ASSOCIATED THEREWITH, SAID ELECTRODE HAVING A THREADED PORTION IN ENGAGEMENT WITH SAID SLEEVE, SAID ELECTRODE HAVING A WRENCH RECESS IN THE TOP SURFACE THEREOF IN AXIAL ALIGNMENT. 